The present invention is directed generally to an electromagnetically responsive particle assembly, and more specifically to a particle assembly having pockets incorporating electromagnetically responsive particles and methods of manufacturing and using the particle assembly.
A variety of products can be made using assemblies (e.g., films, membranes, structures, or other constructions) having electromagnetically responsive particles. Such products include display media, color-changing fabrics, lenses, etc. These assemblies utilize the movement (e.g., rotation or translation) of electromagnetically responsive particles under the influence of an applied electromagnetic field to display information, change color of the assembly, etc. In one approach to fabricating such a particle assembly, bichromal electromagnetically responsive particles rotate under the application of an electromagnetic field to orient one of two colors of the particle""s surface in a viewing direction. The particular color that is oriented towards the viewing direction is dependent on the polarity of the applied electromagnetic field. In a number of applications, the bichromal particles are spherical in shape and are suspended in a dielectric liquid or in a film matrix between two plates.
The full potential of this and other approaches for fabricating assemblies (e.g., films) for flat displays and other applications has not yet been realized. The existing devices suffer from low contrast and low resolution. These devices typically include multiple layers of particles or have particles that are not reliably disposed in optimal packing configurations. In addition, the devices produced to date are thick, thus requiring large operating voltages to produce a sufficiently large electromagnetic field to activate the electromagnetically responsive particles.
Generally, the present invention relates to assemblies containing a substrate with pockets for electromagnetically responsive particles. An arrangement of these pockets can be selected to provide higher particle density than previously realized. One embodiment is an assembly including an assembly substrate and electromagnetically responsive particles. The assembly substrate defines one or more substantially enclosed, fluid-containing cells. Each cell includes pockets in fluid communication with each other. Each pocket is defined by the assembly substrate to hold at least one electromagnetically responsive particle within the pocket.
Another embodiment is an assembly that includes an assembly substrate, particles, and a top coat layer. The assembly substrate defines pockets in the assembly substrate. Each pocket of the assembly substrate corresponds to a pocket formed by ablation of a polymer film. The particles are disposed in the pockets of the substrate and each of the particles is responsive to an applied electromagnetic field to control a state (e.g., a position or orientation) of the particle in the substrate. The top coat layer is disposed over the particles and the substrate.
Yet another embodiment is an assembly having an assembly substrate defining pockets, particles disposed in the pockets, and a first dielectric fluid. Each pocket of this assembly has, on average, at least two of the particles. The particles are colored and are responsive to an applied electromagnetic field to control a state of the particle in the substrate. The first dielectric fluid has a color different than the particles and is disposed in at least a subset of the pockets. Optionally, other dielectric fluids with colors different than the first dielectric fluid and the particles can be disposed in other subsets of the pockets. In addition, the pockets may each contain 25 or more particles.
These assemblies can be used to form a variety of products including, for example, display media (such as thin, portable electronic displays or xe2x80x9celectronic paperxe2x80x9d), traffic and other signage, fabrics (e.g., camouflage or color-changing fabric), lenses, films, roofs (e.g., color changing roofs for decorative or energy absorbing/reflecting purposes), and other products. The particles can be, for example, bichromal particles (e.g., particles with different colored hemispheres), single-colored particles, particles with more than two colors, reflective particles, transparent or translucent particles, particles with a different index of refraction than the assembly substrate, top coat layer, or dielectric fluid around the particles, or particles with transmissive windows. The pockets can be formed in a variety of regular and irregular patterns including, for example, hexagonal or cubic close packed patterns. Assemblies can be formed where the pockets have, on average, about one particle per pocket. Other assemblies can be formed where the pockets have, on average, two or more particles per pocket and, typically, 25 or more particles.
Another embodiment is a method of making an assembly. A polymer film is irradiated to remove a portion of the polymer film by ablation and produce pockets in the polymer film. An assembly substrate with pockets is formed using the polymer film, the pockets of the assembly substrate corresponding to the pockets in the polymer film. Particles are disposed in the pockets of the assembly substrate. Each of the particles is responsive to an applied electromagnetic field to control a state of the particle in the substrate. Finally, a top coat layer is disposed over the particles and at least a portion of the assembly substrate.
This method can be used to form any of the assemblies described above. In some instances, the polymer film is used as the assembly substrate. In other instances, the polymer film is used as a mold from which the assembly substrate is formed.
The above summary of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. The Figures and the detailed description which follow more particularly exemplify these embodiments.